This invention relates to temperature measurement apparatus, and more particularly to apparatus suitable for measuring the temperature of an object optically in a non-contacting manner, the object to have its temperature measured lying within a closed vessel.
As an example of apparatus wherein the temperature of an object to have its temperature measured lies within a closed vessel is measured optically without any contact with the object, there has been known apparatus which measures the temperature of a conductor of a closed bus such as phase segregating bus for use in a power station etc. (Japanese Patent Application Laid-open Specification No. 52-134785).
This apparatus having been hitherto known is constructed of a light projector which emits a light beam, a bimetal element which is mounted on the conductor of the closed bus and which is deformed in response to the temperature change of the conductor, a shield plate which is mounted on the bimetal element and which shields the light beam incident thereon from the light projector, a light receptor which receives the light beam from the light projector, and a decision unit which decides the temperature state of the conductor of the closed bus from the state of the light beam received by the light receptor. The apparatus turns the shield plate owing to the displacement of the bimetal based on the temperature so as to intercept part of the light beam directed from the light projector to the light receptor, and serves to measure the temperature on the basis of the degree of interception of the light beam.
Since the hitherto known apparatus exploits the fact that the bimetal is displaced continuously and rectilinearly relative to the variation of the temperature, it is suitable for measuring the temperature of the object, such as the conductor of the closed bus, which in itself is not affected by vibrations of mechanical oscillations, an earthquake etc. However, it is unsuitable for measuring the temperature of an object which is susceptible to the vibrations, for example, a switch consisting of stationary members and a movable member and lying within a disconnecting switch arranged between a gas-insulated circuit breaker and a bushing. The reason is as follows. The hitherto known apparatus measures the continuous variation of the displacement of the light beam or the quantity of the light by means of the bimetal which is continuously displaced depending upon the temperature. Therefore, when the vibrations such as mechanical oscillations and earthquakes act on the object, they are transmitted to the shield plate mounted on the bimetal as the displacement of the bimetal attached to the object. Thus, the light quantity which the shield plate intercepts changes resulting in an error in the temperature measurement.